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.TH PUTMSG 2 "Nov 1, 2003"
.SH NAME
putmsg, putpmsg \- send a message on a stream
.SH SYNOPSIS
.LP
.nf
#include <stropts.h>

\fBint\fR \fBputmsg\fR(\fBint\fR \fIfildes\fR, \fBconst struct strbuf *\fR\fIctlptr\fR,
     \fBconst struct strbuf *\fR\fIdataptr\fR, \fBint\fR \fIflags\fR);
.fi

.LP
.nf
\fBint\fR \fBputpmsg\fR(\fBint\fR \fIfildes\fR, \fBconst struct strbuf *\fR\fIctlptr\fR,
     \fBconst struct strbuf *\fR\fIdataptr\fR,\fBint\fR \fIband\fR, \fBint\fR \fIflags\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBputmsg()\fR function creates a message  from user-specified buffer(s)
and sends the message to a streams file. The message may contain either a data
part, a control part, or both. The data and control parts to be sent are
distinguished by placement in separate  buffers, as described below. The
semantics of each part is defined by the streams module that receives  the
message.
.sp
.LP
The \fBputpmsg()\fR function does the same thing as \fBputmsg()\fR, but
provides the user the ability to send messages in different priority bands.
Except where noted, all information pertaining to \fBputmsg()\fR also pertains
to \fBputpmsg()\fR.
.sp
.LP
The \fIfildes\fR argument specifies a file descriptor referencing an open
stream. The \fIctlptr\fR and \fIdataptr\fR arguments each point to a
\fBstrbuf\fR structure, which contains the following members:
.sp
.in +2
.nf
int      maxlen;     /* not used here */
int      len;        /* length of data */
void     *buf;       /* ptr to buffer */
.fi
.in -2

.sp
.LP
The \fIctlptr\fR argument points to the structure describing the control part,
if any, to be included in the message. The \fBbuf\fR member in the \fBstrbuf\fR
structure points to the buffer where the control information resides, and the
\fBlen\fR member indicates the number of bytes to be sent. The \fBmaxlen\fR
member is not used in \fBputmsg()\fR (see \fBgetmsg\fR(2)). In a similar
manner, \fIdataptr\fR specifies the data, if any, to be included in  the
message.  The \fIflags\fR argument indicates what type of message should be
sent and is described later.
.sp
.LP
To send the data part of a message, \fIdataptr\fR must not be \fINULL\fR, and
the \fBlen\fR member of \fIdataptr\fR must have a value of 0 or greater. To
send the control part of a message, the corresponding values must be set for
\fIctlptr\fR. No data (control) part is sent if either \fIdataptr\fR
(\fIctlptr\fR) is  \fINULL\fR or the \fBlen\fR member of \fIdataptr\fR
(\fIctlptr\fR) is negative.
.sp
.LP
For \fBputmsg()\fR, if a control part is specified, and \fIflags\fR is set to
\fBRS_HIPRI\fR, a high priority message is sent. If no control part is
specified, and \fIflags\fR is set to \fBRS_HIPRI\fR, \fBputmsg()\fR fails and
sets \fBerrno\fR to \fBEINVAL\fR. If \fIflags\fR is set to 0, a normal
(non-priority) message is sent. If no control part and no data part are
specified, and \fIflags\fR is set to 0,  no message is sent, and 0 is returned.
.sp
.LP
The stream head guarantees that the control part of a message generated by
\fBputmsg()\fR is at least 64 bytes in length.
.sp
.LP
For \fBputpmsg()\fR, the flags are different.  The \fIflags\fR argument is a
bitmask with the following mutually-exclusive flags defined: \fBMSG_HIPRI\fR
and \fBMSG_BAND\fR. If \fIflags\fR is set to 0, \fBputpmsg()\fR fails and sets
\fBerrno\fR to \fBEINVAL\fR. If a control part is specified and \fIflags\fR is
set to \fBMSG_HIPRI\fR and \fIband\fR is set to 0, a high-priority message is
sent. If \fIflags\fR is set to \fBMSG_HIPRI\fR and either no control part is
specified or \fIband\fR is set to a non-zero value, \fBputpmsg()\fR fails and
sets \fBerrno\fR to \fBEINVAL\fR. If flags is set to \fBMSG_BAND\fR, then a
message is sent in the priority band specified by \fIband\fR. If a control part
and data part are not specified and \fIflags\fR is set to \fBMSG_BAND\fR, no
message is sent and 0 is returned.
.sp
.LP
Normally, \fBputmsg()\fR will block if the stream write queue is full  due to
internal flow control conditions. For high-priority messages,  \fBputmsg()\fR
does not block on this condition. For other messages,  \fBputmsg()\fR does not
block when the write queue is full and  \fBO_NDELAY\fR or \fBO_NONBLOCK\fR is
set. Instead, it fails and sets  \fBerrno\fR to \fBEAGAIN\fR.
.sp
.LP
The \fBputmsg()\fR or \fBputpmsg()\fR function also blocks, unless prevented by
lack of internal resources, waiting  for the availability of message blocks in
the stream, regardless of priority  or whether \fBO_NDELAY\fR or
\fBO_NONBLOCK\fR has been specified. No partial message is sent.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fB0\fR is returned. Otherwise, \fB\(mi1\fR is
returned and \fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBputmsg()\fR and \fBputpmsg()\fR functions will fail if:
.sp
.ne 2
.na
\fB\fBEAGAIN\fR\fR
.ad
.RS 16n
A non-priority message was specified, the \fBO_NDELAY\fR or \fBO_NONBLOCK\fR
flag is  set and the stream write queue is full due to internal flow control
conditions.
.RE

.sp
.ne 2
.na
\fB\fBEBADF\fR\fR
.ad
.RS 16n
The \fIfildes\fR argument is not a valid file descriptor open for writing.
.RE

.sp
.ne 2
.na
\fB\fBEFAULT\fR\fR
.ad
.RS 16n
The \fIctlptr\fR or \fIdataptr\fR argument points to an illegal address.
.RE

.sp
.ne 2
.na
\fB\fBEINTR\fR\fR
.ad
.RS 16n
A signal was caught during the execution of the \fBputmsg()\fR function.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 16n
An undefined value was specified in \fIflags\fR; \fIflags\fR is set to
\fBRS_HIPRI\fR and no control part was supplied; or the stream referenced by
\fIfildes\fR is linked below a multiplexor.
.RE

.sp
.ne 2
.na
\fB\fBENOSR\fR\fR
.ad
.RS 16n
Buffers could not be allocated for the message that was to be created due to
insufficient streams memory resources.
.RE

.sp
.ne 2
.na
\fB\fBENOSTR\fR\fR
.ad
.RS 16n
The \fIfildes\fR argument is not associated with a stream.
.RE

.sp
.ne 2
.na
\fB\fBENXIO\fR\fR
.ad
.RS 16n
A hangup condition was generated downstream for the specified stream, or the
other end of the pipe is closed.
.RE

.sp
.ne 2
.na
\fB\fBEPIPE\fR or \fBEIO\fR\fR
.ad
.RS 16n
The \fIfildes\fR argument refers to a streams-based pipe and the other end of
the pipe is closed.  A \fBSIGPIPE\fR signal is generated for the calling
thread. This error condition occurs only with SUS-conforming applications. See
\fBstandards\fR(7).
.RE

.sp
.ne 2
.na
\fB\fBERANGE\fR\fR
.ad
.RS 16n
The size of the data part of the message does not fall within the range
specified by the maximum and minimum packet sizes of the topmost stream module.
This value is also returned if the control part of the message is larger than
the maximum configured size of the control part of a message, or if the data
part of a message is larger than the maximum configured size of the data part
of a message.
.RE

.sp
.LP
In addition, \fBputmsg()\fR and \fBputpmsg()\fR will fail if the stream head
had processed an asynchronous error before the call.  In this case, the value
of \fBerrno\fR does not reflect the result of \fBputmsg()\fR or \fBputpmsg()\fR
but reflects the prior error.
.sp
.LP
The \fBputpmsg()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The \fIflags\fR argument is set to \fBMSG_HIPRI\fR and \fIband\fR is non-zero.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.sp
.LP
.BR Intro (2),
.BR getmsg (2),
.BR poll (2),
.BR read (2),
.BR write (2),
.BR attributes (7),
.BR standards (7)
.sp
.LP
\fISTREAMS Programming Guide\fR
